English Medium Class 9 - CBSE Question Bank Solutions for Science

A liquid compound X of molecular mass 18 u can be obtained from a number of natural sources. All the animals and plants need liquid X for their survival. When an electric current is passed through 200 grams of pure liquid X under suitable conditions, then 178 grams of gas Y and 22 grams of gas Z are produced. Gas Y is produced at the positive electrode whereas gas Z is obtained at the negative electrode. Moreover, gas Y supports combustion whereas gas Z burns itself causing explosions.

1. Name (i) liquid X (ii) gas Y, and (iii) gas Z.
2. What is the ratio of the mass of element Z to the mass of element Y in the liquid X ?
3. Which law of chemical combination is illustrated by this example ?
4. Name two sources of liquid X.
5. State an important use of Y in our life.

Define ‘formula mass’ of a compound.

State whether the following statements are true or false:

A sodium ion has positive charge because it has more protons than a neutral atom.

State whether the following statements are true or false :

A chloride ion has negative charge because it has more electrons than a neutral atom.

What is the name of a particle which contains 10 electrons, 11 protons and 12 neutrons ?

Name the particle which has 18 electrons, 18 neutrons and 17 protons in it.

Fill in the following blank with suitable word :

The particle which is formed by the gain of electrons by an atom is called ..............

Fill in the following blank with suitable word:

The particle which is formed by the loss of electrons by an atom is called..............

Fill in the following blank with suitable word:

The particle which is formed by the loss or gain of electrons by an atom is called..............

Fill in the following blank with suitable word:

A potassium ion has positive charge because it contains less............... than.....................

Fill in the following blank with suitable word:

A sulphide ion has negative charge because it contains less ....................... than ...................

An element X has a valency of 2. Write the simplest formula for bromide of the element.

An element X has a valency of 2. Write the simplest formula for oxide of the element.

What is the difference between a cation and an anion ? Explain with examples.

The valencies (or charges) of some of the ions are given below :

Ion            Valency        Ion                Valency                        (Charge)                             (Charge)

Sodium ion       1+      Nitrate ion            1–  
Copper ion       2+       Sulphide ion         2–

Using this information, write down the formulae of :

1. Sodium sulphide
2. Copper nitrate

Explain the formation of (i) sodium ion, and (ii) chloride ion, from their respective atoms giving the number of protons and number of electrons in each one of them. What is the reason for positive charge on a sodium ion and a negative charge on a chloride ion ?

A particle X has 17 protons, 18 neutrons and 18 electrons. This particle is most likely to be :

An element has an atomic number 12. How many electrons will be present in the K, L and M energy shells of its atom?

A particle P has 18 electrons, 20 neutrons and 19 protons. This particle must be :

What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.